The normal function of a slack adjuster, especially for a railway vehicle brake rigging, is to prolong itself in relation to the wear of the brake blocks or the like due to relative rotation between different parts therein. For example at the replacement of wornout brake blocks, it is necessary to manually bring back the slack adjuster to its original length by rotating said different parts therein relative to each other in the direction for shortening the adjuster.
This may be accomplished in that two parts, which normally are non-rotatably held together by a clutch arrangement under the action of a spring, are manually rotated relative to each other.
A typical example of this prior art solution is shown in our U.S. Pat. No. 2,793,716, FIG. 4, where an adjuster ear and an adjuster tube normally is held in clutch engagement by means of a spring.
In some cases, however, it is inconvenient or even impossible to rotate the manually rotatable part full turns to accomplish the shortening of the adjuster. It may for example due to limited space available only be possible to rotate the part 20.degree.-30.degree. with an external tool before a new hold must be taken.